1. Field of the Invention
The present invention relates to an organic thin film transistor, a method of fabricating the same, and a gate insulating layer used in the same and, more particularly, to an organic thin film transistor comprising an azole-metal complex compound, a method of fabricating the same, and a gate insulating layer used in the same.
2. Description of Related Art
Thin film transistors (TFTs) are fundamental components in contemporary electronics, including, for example, sensors, image scanners, and electronics display devices. Usually, in manufacturing a display device, cost is a critical point directing the development of the research. Manufacturers urge that high quality displays should also be produced with a lower cost.
Organic thin film transistors (OTFTs) are advantageous in their low producing cost, rollability, and large area and have drawn much attention of the researchers. OTFTs can be divided into top contact OTFTs and bottom OTFTs according to their structure. A top contact OTFT is generally composed of a substrate 10; a gate electrode 11 formed on the substrate 10; a gate insulating layer 12 formed on the gate electrode 11, an organic semiconductor layer 13 formed on and covering the whole gate insulating layer 12, and a source electrode 14 and a drain electrode 15 formed on the organic semiconductor layer 13, as shown in FIG. 1.
Referring to FIG. 2, in which a bottom contact OTFT is shown, a conventional bottom contact OTFT is generally composed of a substrate 10; a gate electrode 11 formed on the substrate 10; a gate insulating layer 12 formed on the gate electrode 11; a source electrode 14 and a drain electrode 15 formed on the gate insulating layer 12; and an organic semiconductor layer 13 formed on and covering the source electrode 14, the drain electrode 15, and the gate insulating layer 12.
According to a conventional method of forming a gate insulating layer of an OTFT, coating process or printing process is usually applied. However, the cost of the equipment for these processes is high, and the uniformity of the obtained coated film cannot be satisfied when applied to large area production, and moreover, excessive steps of photolithography should be taken when a coating process is applied. The maintenance cost of the precision instrument for printing process is a great burden. Therefore, many efforts have been spent on developing a novel OTFT that can be fabricated in a low-cost, simple, and environmentally-friendly method.
Azole compounds such as imidazoles, benzimidazoles, or benzotriazoles have been widely used in the organic solderability preservation (OSP) coatings in the conventional printed circuit board manufacturing process and in the soldering materials of chip packaging process (see U.S. Pat. Nos. 5,858,074, 3,295,917, 3,891,470, 3,933,531, 4,373,656, and 5,173,130). OSP coatings are used to provide protection against copper solderability degradation caused by various process steps in fabrication process such as exposure to multiple heat cycles during electronic component fabrication for surface mount technology and mixed technology printed wiring boards assembly.
However, there is no mention about applying such azole compounds to the forming of the gate insulating layer in an electric element such as transistors. Unlike organic solderability preservation (OSP) coatings, insulating layers are more difficult to be formed. Electrical characteristics, which may be largely influenced by the thickness, surface roughness, composition of the insulating film, are the main requirements that should be taken into consideration instead of physical characteristics such as protecting ability. If a new material is applied but destroys the original function of the electrical element such as transistors, the induction of such material fails. Therefore, the technique of forming the insulating layer is more difficult than that of forming the organic solderability preservation (OSP) coatings.
In fact, many prior arts have disclosed the usage of azole compounds in the forming of organic solderability preservation (OSP) coatings, however none of them ever taught the forming of an insulating layer with azole compounds.